Ontogeny of Crown Bud Clusters and Dormancy-breaking Treatments Influence Productivity and Spread of Harvest Maturity of Gentian ‘Showtime Diva’

Abstract

<jats:p>Cut flower productivity and quality of gentian is associated with growth and development of crown buds. Experiments were carried out with the gentian cultivar Showtime Diva to identify the response to treatments that break dormancy [cold temperature (chilling), gibberellic acid (GA<jats:sub>3</jats:sub>)] applied at different stages of development of crown buds (plants with nonemerged crown buds, shoots recently emerged, or shoots emerged and elongated). The comparative growth potential of crown buds within the cluster was also investigated. At the stages of development examined, the application of GA<jats:sub>3</jats:sub> (100 ppm) increased emergence of crown buds as shoots, leading to development of more flowering shoots. A similar response was observed with exposure to cold, but only on plants with nonemerged crown buds. Shoot emergence increased in response to increased duration of cold from 0 to 42 days (5 °C). Both chilling and GA<jats:sub>3</jats:sub> could potentially be used to reduce the duration to, and spread of, harvest maturity if applied before shoot emergence. The hierarchical relationship of buds in crown bud clusters led to differential responses to application of GA<jats:sub>3</jats:sub>. Buds ontogenetically positioned at the proximal end of the bud cluster took a similar duration to reach shoot emergence or harvest maturity. For buds located at the distal end there was a positive correlation between ontogenetic bud position and the duration to reach shoot maturity. Shoot length and number of nodes at harvest maturity showed slight negative correlations with the position of the bud in the bud cluster. The results provide an explanation for possible sources of the variation in quality and quantity of floral shoots, and spread in time to harvest maturity within a single plant, and with development stage.</jats:p>

Shortening the Production Cycle of Clematis

“…1, a greater number of shoots per plant occurred with the increasing duration of cold from 0 to 9 weeks. A similar response was observed for hybrid gentian: shoot emergence increased in response to the increased duration of cold from 0 to 42 d at 5 °C (Samarakoon et al, 2016). For most temperate climate species, the main factor governing the breakage of dormancy in buds is exposure to low temperatures to satisfy chilling requirements (Lang et al, 1987).…”

“…1). A reduced duration to harvest maturity following exposure to cold treatment was also noted for other herbaceous perennials, such as gentian hybrids (Samarakoon et al, 2016), Helleborus sp. (Christiaens et al, 2012), and Lavandula angustifolia (Whitman et al, 1996).…”

“…As noted during the current study (Expt. 1) and for other plant species (Harvey and Nowierski, 1988;Ku et al, 2007;Samarakoon et al, 2016), the inadequate accumulation of chilling can result in delayed budbreak, decreased percentages of buds forming shoots, and slow or weakened shoot growth. For commercial application purposed, it will be important to quantify the chilling requirement and the corresponding plant responses of other cultivars of clematis because varieties may respond differently, as also noted for other plant species (Gariglio et al, 2006).…”